Andrew J. Macpherson is Professor of Medicine and Director of Gastroenterology at the University Hospital of Bern, Switzerland. He studied Biochemistry and Medicine at Cambridge University and did his PhD on sugar-proton symport systems in the laboratory of Sir Hans Kornberg and Peter Henderson. His clinical medical studies and clinical speciality training in Gastroenterology were in Cambridge and London. The results (of control experiments) during a project in London on immune-mediated damage to intestinal epithelial cells focused his interest on the way in which the mucosal immune system responds to commensal intestinal microbes. In 1997 he moved to work with Rolf Zinkernagel at the Institute of Experimental Immunology in Zürich. Between 2004 and 2008 he was Farncombe Professor of Medicine and a Canada Research Chair holder at McMaster University in Hamilton.His work has shown that there are different pathways of induction of immunoglobulin (Ig)A in the intestinal mucosa by commensal intestinal microbes, with and without help from T cells. He has also shown a compartmentalisation between the mucosal and systemic Ig responses to commensals, since mucosal immune responses are driven locally in the mucosal compartment by dendritic cells that have sampled commensals at the epithelial surface. More recently his lab has developed methods of reversible colonisation of germ-free mice to allow intestinal colonisation with commensals and mucosal immune priming to be experimentally uncoupled, to address mucosal immune memory and the functional consequences of mucosal immune responses in host-microbial mutualism.

Healthy humans and other animals have enormous numbers of bacteria and other microorganisms in the lower intestine. These are very good for us as they help us harvest energy from food, provide us with vitamins, break down toxic chemicals and prevent pathogenic bacteria from causing disease. For health, these commensal microbes must be contained inside the intestinal tube, but allowed to flourish. In this project we will study the way in which the main antibody of the body, IgA, is secreted into the intestine to promote the peaceful coexistence of intestinal commensal bacteria and the host. We will focus on how live microbes are prevented from entering the tissues of the body, yet provided with the right environment next to the intestinal membrane to form stable growing communities.